• 한국안전학회지
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• 제27권2호
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• pp.111-116
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• 2012

This study deals with the traffic accidents of circular intersections in Korea. The purposes are to comparatively analyze the characteristics by operational type, and to develop the models using the data of 82 intersections. In pursuing the above, this study gives particular emphasis to modeling such the accidents as the roundabout and rotary in urban area. The main results analyzed are as follows. First, the null hypotheses that the number of accidents are the same in both the urban and rural intersections, and roundabout and rotary in urban area, were analyzed to be rejected. Second, 3 accident models were developed, which were all statistically significant. The independent variables used in the above models are the ADT, number of approach lane, bus stop, parking facilities, and others. This study could be expected to give some implications to the traffic safety policy decision-making.

• 대한교통학회지
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• 제32권1호
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• pp.73-81
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• 2014

이 연구는 고속도로에서 발생한 교통사고에 대한 기하구조의 영향을 알아보고자 시도되었다. 기하구조의 경우에는 지침 등에서 정하는 기준 권장값등이 있지만, 기존의 사고모형에서는 교통사고에 영향을 미치는 기하구조의 자료가 통합된 형태로 사용되어 혼합된 형태로 설치된 현실을 추정된 모형이 제대로 설명하지 못하는 단점이 있다. 따라서 이 연구에서는 기하구조를 기준값에 의해 세분화된 기하구조 자료를 사용함으로써, 현실을 반영한 모형을 추출하고자 하였다. 그리고 각 기하구조별 탄력성 분석을 통해 사고에 미치는 영향을 제시하였다. 이는 향후 교통안전을 고려한 기하구조의 지침 정립에 도움이 될 것으로 사료된다.

• 응용통계연구
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• 제31권4호
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• pp.475-484
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• 2018

감마 일반화 선형모형은 음이 아니며 치우침이 있는 반응변수에 유용한 모형으로 알려져 있다. 그러나 포아송 분포 또는 이항 분포에 기반한 일반화 선형모형에 비해 적은 관심을 받아왔다. 특히, 회귀계수의 유의성 검정에 대해서는 연구가 면밀히 되어 있지 않다. 본 논문에서는 감마 일반화 선형 모형의 검정에 대해 다양한 통계량들을 알아보고 수치 연구를 통해 그들의 성능을 비교한다. 수치 실험의 결과 부분 이탈도 검정 방법의 문제점이 나타났으며, 가능도비 검정 방법과 F-검정 방법이 좋은 성능을 보임을 확인하였다.

• 한국IT서비스학회지
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• 제10권4호
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• pp.191-204
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• 2011

Recently, many software companies are trying to improve the software quality and project outcome with more costs and efforts in development time. In the software convergence and integration environments, it is required efforts to gain high quality of software. In other words, it is required to utilize software engineering knowledge and technology for higher software quality and better software project productivity. The Software development productivity can be varied by software process capability according to building a framework for software development, selection and use of appropriate technology, human resource management. Software process capability will influence software project outcome which is the general opinion. This study provides empirical evidence about software engineering efforts and investment approach to lead software project performance. We measured the software engineering efforts by SW engineering level and analyzed the corelation between software engineering level and schedule deviation. And, we verified that this performance is affected by the size of software company. As a result, software process capability is important to build a infrastructure and develop systematically software project. The higher software engineering level can lead to improved software project performance.

• 한국안전학회지
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• 제32권6호
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• pp.131-136
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• 2017

This study deals with the small-size roundabout accidents. The purpose of this study is to analyze the characteristics of small-size roundabout accidents from developing various types of accident models, and to discuss the improvement countermeasures by vehicle type. The geometric characteristics of 36 roundabouts are surveyed, and the traffic accident data from 2008 to 2014 are collected and classified as those of car, truck and motor cycle. In this study, dependent variable is the number of accident and independent variables are such 15 variables as geometry and traffic volume. The main results are as follows. First, the null hypotheses that the size of roundabout and type of vehicle are not related to traffic accident are rejected. Second, 8 count data models which are all statistically significant are developed. Third, the number of circulatory roadway lane and sidewalk are selected as common variables of roundabout size. Finally, the number of entry and circulatory roadway lane are selected as common variables of vehicle type.

• 한국안전학회지
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• 제32권3호
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• pp.123-129
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• 2017

This study deals with the traffic accident of truck at circular intersection. The purpose of this study is to develop the truck accident models based on type of accident and conflict. In pursuing the above, the study gives particular attentions to selecting the appropriate models among Poisson and Negative binomial models using statistical program LIMDEP 8.0. The traffic accident data from 2007 to 2014 are collected from TAAS data set of Road Traffic Authority. Such the dependent variable as number of truck accidents and the 24 independent variables as geometry, traffic volume and others are used. The main results are as follows. First, 5 Poisson models (${\rho}^2$ of 0.164~0.351) which are all statistically significant are selected. Second, the common variable based on type of accident and conflict is analyzed to be truck apron width. The specific variables are, however, evaluated to splitter island, area of splitter island, speed limit sign, truck apron, number approach road, circular intersection sign, speed hump and traffic volume. Finally, widening the truck apron width and improving the above specific variables are analyzed to be important for truck accident reduction at circular intersections.

• 한국안전학회지
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• 제33권3호
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• pp.77-82
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• 2018

This paper aims to analyze the accident based on changing patterns of traffic culture index. For this purpose, this paper particularly focuses on classifying the traffic culture patterns and developing the traffic accidents using panel count data model. The main results are as follows. First, the traffic culture patterns are divided into 'increasing', 'decreasing' and 'other' patterns. The null hypotheses that the number of accident are the same over patterns are rejected. Second, 4 fixed effect negative binomial models which are all statistically significant are developed. Third, the regions with 'increasing' pattern are analyzed to be mostly the counties, and to demand the traffic law enforcement. Fourth, the regions with 'decreasing' pattern are evaluated to be mainly the districts and to require such the traffic culture as turn signal usage. Finally, the regions with 'other' pattern are analyzed to be mostly the cities and to ask for enhancing the level of traffic culture.

• 한국도로학회논문집
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• 제17권6호
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• pp.65-73
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• 2015

PURPOSES : This study tries to develop the accident models of 4-legged signalized intersections in Busan Metropolitan city with random parameter in count model to understanding the factors mainly influencing on accident frequencies. METHODS : To develop the traffic accidents modeling, this study uses RP(random parameter) negative binomial model which enables to take account of heterogeneity in data. By using RP model, each intersection's specific geometry characteristics were considered. RESULTS : By comparing the both FP(fixed parameter) and RP modeling, it was confirmed the RP model has a little higher explanation power than the FP model. Out of 17 statistically significant variables, 4 variables including traffic volumes on minor roads, pedestrian crossing on major roads, and distance of pedestrian crossing on major/minor roads are derived as having random parameters. In addition, the marginal effect and elasticity of variables are analyzed to understand the variables'impact on the likelihood of accident occurrences. CONCLUSIONS : This study shows that the uses of RP is better fitted to the accident data since each observations'specific characteristics could be considered. Thus, the methods which could consider the heterogeneity of data is recommended to analyze the relationship between accidents and affecting factors(for example, traffic safety facilities or geometrics in signalized 4-legged intersections).

• 한국도로학회논문집
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• 제13권1호
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• pp.13-19
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• 2011

본 연구의 목적은 가로구간 사고특성을 분석하고 주 야간 사고모형을 개발하는데 있다. 이를 위해 청주시 가로구간 24개 도로를 연구대상으로 2007년 사고 자료를 이용한다. 연구의 주요결과는 다음과 같다. 첫째, 가로구간의 주간 사고건수가 야간 사고건수보다 많았지만, 사고율에서는 야간사고율이 높은 것으로 분석되었다. 둘째, 4개의 사고모형이 개발되었으며, 이들은 통계적으로 모두 유의한 것으로 분석되었다. 마지막으로, 모형에 채택된 독립변수를 활용하여 주 야간 사고모형의 차이가 비교 분석되었다.

• Communications for Statistical Applications and Methods
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• 제25권2호
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• pp.173-184
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• 2018

In medical or public health research, it is common to encounter clustered or longitudinal count data that exhibit excess zeros. For example, health care utilization data often have a multi-modal distribution with excess zeroes as well as a multilevel structure where patients are nested within physicians and hospitals. To analyze this type of data, zero-inflated count models with mixed effects have been developed where a count response variable is assumed to be distributed as a mixture of a Poisson or negative binomial and a distribution with a point mass of zeros that include random effects. However, no study has considered a situation where data are also censored due to the finite nature of the observation period or follow-up. In this paper, we present a weighted version of zero-inflated Poisson model with random effects accounting for variable individual follow-up times. We suggested two different types of weight function. The performance of the proposed model is evaluated and compared to a standard zero-inflated mixed model through simulation studies. This approach is then applied to Medicaid data analysis.